java day23 swings

8/6/2019 Java Day23 Swings

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The javax.swing package contains

several classes used for creating Menus JMenuBar, JMenu, JMenuItem (and variants):

y JRadioButtonMenuItem

y JCheckboxMenuItem

Only the JMenuItem objects (and variants)generate events.

Edit View Help


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JMenuItems generate

Action EventsSome Events and Their Associated Event Listeners

Act that Results in the Event Event Listener Type

Action: User clicks a button, presses Enter while

typing in a text field, or chooses a menu itemActionListener

User closes a frame (main window) WindowListener

User presses a mouse button while the cursor is

over a componentMouseListener

User moves the mouse over a component MouseMotionListener

Component becomes visible ComponentListener

Component gets the keyboard focus FocusListener

Table or list selection changes ListSelectionListener

Any property in a component changes such as

the text on a labelPropertyChangeListener


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JMenuBar

JMenuBar is a bar where the menus are

placed.

y There is only one menu bar per frame.

JMenuBar

Edit View HelpFile


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JMenu

JMenu (such as File or Edit) is a group of

menu choices.

y A JMenuBar object may include many JMenu

objects.

JMenu


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JMenuItem JMenuItem (such as Copy, Cut, or Paste) is an

individual menu choice in a JMenu object.

Action command defaults to text of menu item

y Override with call to setActionCommand()

y

Useful when providing UI in multiple languages

JMenuItem

JSeparator


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Demo on Menus


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Sequence for Creating Menus

1. Create a JMenuBar object and add it to a

frame via setJMenuBar()

2.Create a JMenu object.

3. Create JMenuItem objects and add them

to the JMenu object.

4. Add the JMenu object to the JMenuBar

object.


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Radio buttons & Check boxes

Along with JButton, Radio buttons and

Check boxes are all specific kinds of

buttons they all derive from the

AbstractButton class

y This is called inheritance coming soon

This implies similar behavior for these

classes


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Radio Buttons

Implemented byJRadioButton

A GUI usually prevents

more than one Radiobutton to be selected atonce

y Typically used along with aButtonGroup object

y ButtonGroup takes care ofdeselecting the previousRadio button when a newone is selected


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Mouse Events

Mouse events arise from suchuser interactions as

y moving the mouse

y dragging the mouse (moving the

mouse while the mouse button is

being pressed)

y clicking the mouse buttons.

Who listens for Mouse Events?y JFrame

y

ContentPaney or whoever is interested in getting

events


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Handling Mouse Events

A MouseListener handles most mouse events:y mouseEntered cursor crossed into the boundary

y mouseExited cursor crossed out of the boundary

y mousePressed button down (specifics in MouseEvent)

y mouseReleased button up

y mouseClicked button down/up in quick succession

A MouseMotionListener handles mouse movement

y mouseDragged mouse moved while button down

y mouseMoved mouse moved while button up

Point location info in MouseEvent Location is relative to the listening components origin


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JTabbedPane

A component that lets the user switch between

a group of components by clicking on a tab with

a given title and/or icon Constructors

y JTabbedPane()

Adding Tabs:

y addTab(tabname,component)

Places the specifiedcomponentinto the tablandgives it the specified

name.


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Tab 1 has the label

Tab 2 has the panelcontaining a label

and a text field


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JScrollPane

Provides a scrollable view of any

lightweight Swing component

Constructor

y JScrollPane(anyComponent)


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The Vector Class

in the java.util package resizable array containing references to Object

instances (or instances of Object subclasses)y Can be indexed

y Can have elements added and deleted

Some useful methods:y elementAt(int) returns the object referenced by specified

element

y addElement(Object) adds the object to the end of the Vector

y removeElementAt(int) deletes the element at the specified

indexy removeAllElements() empties out the vector


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Here we set up the

column-header

vector by adding

strings to it.

There will be a totalof four columns in

this example.


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In order to ensure

that the JTable is

scrollable, we put itinto a JScrollPane.

We add the

JScrollPane to the

frame instead of

directly adding theJTable to the frame.


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java day23 swings

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